Air conditioner not working most of the time.

We have changed the compressor. We have preformed a leak test. The belt is in good condition and compressor is working fine as far not going on and off all the time. I replaced the fan cellenoid that is on the side in the engine comp under the air cleaner. Now the fans work good. The other day we took a drive, to check out the car. ( We are taking a trip to texas. We live in washington) We have been working on the air conditioning for a time now and thought that we had solved the problem, but on the drive it stated to get warm air out the vents. Cool air but not cold. We started home after dark and the air was colder at night but not cold like it should be. Now this morning it is not cool at all. But has pressure in the system. HELP! Thanks Gary